Structure of the Mannose-Rich Oligosaccharide Chains of Concanavalin A-Binding Glycopeptides Derived from Beef Brain Glycoproteins

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Abstract
A neutral, mannose-rich, concanavalin A (ConA)-binding glycopeptide fraction was obtained by proteolytic digestion of defatted beef brain tissue. Hydrazinolysis followed by gel filtration of the reaction products provided 3 oligosaccharides. A portion of each oligosaccharide was treated by exhaustive digestion with .alpha.-mannosidase. Another portion was subjected to selective acetolysis of Man.alpha.1 .fwdarw. 6Man linkages, providing 2 fragments that were recovered by gel filtration. The structure of the intact oligosaccharides, as well as the fragments obtained by selective acetolysis and enzymatic treatment, were resolved by GLC-mass spectrometric analysis. The structures of the 3 oligosaccharides were: Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3)Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 3)Man.beta.1 .fwdarw. 4-N-acetylglucosamine (GlcNAc).beta.1 .fwdarw. 4N-acetylglucosaminitol (GlcOLNAc); Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 2 Man.alpha.1 .fwdarw. 3)Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3)-Man.beta.1 .fwdarw. 4GlcNAc.beta.1 .fwdarw. 4GlcOLNAc; and Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3) Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3)Man.beta.1 .fwdarw. 4GlcNAc-.beta.1 .fwdarw. 4GlcOLNAc. These structures account for 15-20% of the glycoprotein-carbohydrate of whole beef brain and most of the oligosaccharides that demonstrate a high affinity for ConA. In view of the large number of ConA-binding glycoproteins in brain tissue, it appears that many of these different glycoproteins must contain structurally identical oligosaccharides.